The present invention relates to a compressor for compressing a refrigerant gas by a compressor element adapted to be rotated by an electric motor.
FIG. 8 shows a schematic illustration of a conventional refrigerating cycle as disclosed in Japanese Patent Laid-Open Publication No. 58-211587, for example. The refrigerating cycle includes a rotary compressor 1, a condensor 2, a solenoid valve 3, a capillary tube 4, an evaporator 5 and a check valve 6.
When the compressor 1 starts operating, a refrigerant gas compressed is fed to the condeser 2 in a direction shown by an arrow, and is condensed by the condenser 2. Then, the refrigerant gas condensed is fed to the evaporator 5, and is evaporated by the evaporator 5 is conduct a refrigerating operation. The evaporated gas is then returned to the compressor 1. When the compressor 1 is stopped, the solenoid valve 3 is operated to cut a part of a high-pressure circuit of the refrigerating cycle, and the check valve 6 is operated to cut a part of a low-pressure circuit. Under the stopped condition of the compressor 1, a large amount of high-temperature and high-pressure gas in a closed container flows through the condenser 2, the capillary tube 4 and the evaporator 5, and also flows through sealing portions of parts of the compressor element in the closed container into a cylinder, an intake pipe and the evaporator 5 (so that pressure and temperature in the circuit may be balanced), which will cause an increase in heat load of the refrigerating cycle to reduce an efficiency of the refrigerating cycle. The above-mentioned cutting of the circuit by the solenoid valve 3 and the check valve 6 is intended to suppress the reduction in the efficiency of the refrigerating cycle.
FIG. 9 shows another example of the conventional refrigerating cycle carrying out the same operation as the above shown in FIG. 8, utilizing a change in pressure differential across the check valve 6. The refrigerating cycle includes a pressure differential valve 7 adapted to be operated by pressure signals from signal tubes 8 and 9 connected to both sides of the check valve 6, which valve 7 usually incorporates a diaphragm. The pressure differential valve 7 detects a high-pressure signal (discharge side) and a low-pressure signal (intake side). After stoppage of the compressor 1, a low pressure (pressure between the compressor 1 and the check valve 6) is increased to almost balance with a high pressure on one side of the diaphragm. Such a displacement of the diaphragm is utilized to operate valve members provided in the high-pressure and low-pressure circuits.
FIG. 10 shows a further example of the conventional refrigerating cycle having th same function as above, using an integral type pressure differential valve 10 including a check valve assembled with a pressure differential valve.
In the above-mentioned various refrigerating cycles, the solenoid valve 3, the pressure differential valve 7 or the integral type pressure differential valve 10 is used for the purpose of preventing a reverse current of the refrigerant gas upon stoppage of the compressor 1. In the casing of the solenoid valve 3, the solenoid valve itself consumes a power to reduce the efficiency of the refrigerating cycle. In the case of the pressure differential valve 7 or the integral type pressure differential valve 10, a signal piping and an operational structure are complicated to cause a defective operation. Further, the number of welding portions is increased to cause leakage of the refrigerant gas, thus reducing the reliability. Additionally, costs for manufacturing and assembling these control valves are increased.